A method for producing granulated nitrogen-potash fertilizer is known that comprises mixing a concentrated ammonium nitrate solution with potassium chloride, granulating the mixture with a magnesium salt, and drying the product (patent of the Russian Federation, RU 2225384 C1, IPC CO5G1/00, CO5C1/00, CO5D1/00, published on 10 Mar. 2004). In the known method, the magnesium salt, which is magnesium nitrate, is added to the mixture or to the concentrated solution to reduce caking of the granulated product. However, caking of the product increases during its storage. Performance characteristics of the product (strength of granules and caking ability) are low since in the final product, processes of conversion of raw materials (conversion of ammonium nitrate and potassium chloride into potassium nitrate and ammonium chloride) continue to run.
Another known method for producing nitrogen-potash fertilizers comprises mixing an ammonium nitrate melt with potassium chloride, granulating the mixture comprising magnesium sulfate in a granulating drum, and drying the product (patent of the Russian Federation, RU 2154620 C1, IPC CO5C1/02, CO5D1/00, CO5G1/06, CO5D5/00, published on 20 Aug. 2000). The method for producing nitrogen-potash fertilizers on the basis of ammonium nitrate and potassium chloride is characterized by insufficient productivity due to frequent shutdown of the equipment for cleaning because of its plugging and clogging with the product. The granulated product produced by the known method has a low strength granules and a high caking ability; long-term storage provides the formation of adhered agglomerates; the content of a dust fraction increases during a long-term transportation because of crushing granules; and processes of conversion of raw materials (ammonium nitrate and potassium chloride) continue to run in the final product.
The closest prior art for the claimed invention is a method for producing granulated nitrogen-potash fertilizers, comprising mixing a concentrated ammonium nitrate solution with potassium chloride and ammonia, granulating the mixture in a granulating drum, and drying the product (patent of the Russian Federation, RU 2275347 C1, IPC CO5C1/02, CO5D1/00, CO5G1/00, published on 27.04.2006 (prototype)). The known method is characterized by a high conversion degree of ammonium nitrate and potassium chloride into potassium nitrate and ammonium chloride, respectively, which provides high agrochemical properties of the produced granulated nitrogen-potash fertilizers. However, the product granules have insufficient strength, as a result of which a portion of fine-grained fraction increases during a long-term transportation, thereby increasing caking during a long-term storage.